Abstract: China's high-speed railway is at the critical period of the constructing of new alignments and maintenance the existing lines. The operation and maintenance of railway are of great significance. Some of the induced hazards, which might affect the safe operation of the high-speed rail lines, have been observed at the high-speed rail tunnels, especially, the seasonal freeze-thaw related hazards in the frozen soil areas. These hazards included cracks at the tunnel lining structures, spalling of concrete, seepage at tunnel crests and separation of tunnel structure and adjacent geomaterials, etc. This paper presents a hazard investigation of a tunnel near Longjia Airport at Changchun-Jilin Inter City High-Speed Rail Line. Reasons that resulting these hazards and in-situ testing and evaluation methods are discussed in the paper. The results indicate that, the ponded groundwater was accumulated underneath the mat foundation at different locations and it is possible these isolated water accumulation areas might inter-connected. The test results were consistent with the visual inspections.

Key words: High-speed Railway Tunnel, Tunnel Crest Hazards, Frost Damage, Elastic Wave Propagations